I have a Telford Direct 900mm x 450mm copper cylinder with 1xbacker Kw 240V type 311 and 1xbackersafe 3Kw 240V ~2.76Kw 230V type BS311C immersion heaters. I noticed the water getting progressively cooler over a period of a couple of days until it was just plain cold. I have since turned off the swit...
